1. Field of the Invention
The present invention generally relates to liquid supply devices and liquid cartridges.
2. Description of Relate Art
A known ink cartridge, e.g., an ink cartridge described in JP-A-2008-221698, is configured to removably attach to an inkjet recording apparatus. The known ink cartridge has an ink chamber formed therein, and ink stored in the ink chamber is supplied to the inkjet recording apparatus when the ink cartridge is attached to the inkjet recording apparatus. A sensor arm is positioned in the ink chamber. When the ink surface in the ink chamber lowers as the amount of ink in the ink chamber decreases, a float portion provided at one end of the sensor arm moves downward with the lowering ink surface, such that the sensor arm pivots to move an indicator portion positioned at the other end of the sensor arm. Thus, when the amount of ink remaining in the ink chamber is greater than or equal to a predetermined amount, the indicator portion is positioned in a particular space provided in the ink chamber, and when the amount of ink is less than the predetermined amount, the indicator portion is positioned away from the particular space. By detecting the movement of the indicator portion with an optical sensor, e.g., a photo-interrupter, provided in the inkjet recording apparatus, it is possible to determine that the remaining amount of ink in the ink chamber has become less than the predetermined amount.
The position of the optical sensor may vary due to manufacturing errors or the like, and therefore the position at which the optical sensor detects the indicator portion for determining the remaining amount of ink in the ink chamber may vary. As a result, the level of ink at which the remaining amount of ink in the ink chamber is determined to be less than the predetermined amount may vary.
Due to the variation in the level of ink at which the remaining amount of ink is determined to be less than the predetermined amount, it may be determined that the remaining amount of ink has become less than the predetermined amount and the inkjet recording apparatus may instruct a user to replace the ink cartridge even though an amount of ink still remains. In another case, the remaining amount of ink may not be determined to be less than the predetermined amount and the inkjet recording apparatus may continue printing, even though only very little amount of ink remains, until ink is completely used up. This may deteriorate the print quality or the inkjet recording apparatus may fail to perform printing.